import java.util.Scanner;

/**
 * Created with IntelliJ IDEA.
 * Description:
 */
public class TestDemo {
    public static void main(String[] args) {
        Scanner scanner = new Scanner(System.in);
        int n = scanner.nextInt();
        int ret = 0;
        ret = fib(n);
        System.out.println(ret);
    }

    public static int fib(int n){
        if(n == 1 ||n == 2){
            return 1;
        }else {
            return fib(n-1)+fib(n-2);
        }
    }
}
